Various methods have conventionally been proposed as a control system design method and a theoretical system thereof has been already established. In the design based on the classical control theory, however, its target is directed to a control system having one input and one output so that, in order to control a plurality of states at the same time, a control device relating to the most inner state is designed for each state, a control device for the outer loop is designed outside of the most inner state, and so on. That is, there has been employed a multi-looped control system configuration. More specifically, when targets to be controlled are Gp1 and Gp2 as shown in FIG. 3, a control device Gc2 is first designed for the control target Gp1, the control device Gc2 is then designed for a loop system of the control target Gp1 and a control device Gc1 and for a control system of the control target Gp2, and an output thereof is given as a target value of the control device Gc1. Similarly, when there is an outer loop not illustrated, a control device Gc3 is designed for an object Gp3 to be controlled, an output thereof is given as a target value of the control device Gc2, and so on. In this way, design is carried out sequentially from an innermost system to an outer system to form a multiple loop configuration.
It is well known in such a control method that, if an inner control system does not have a response higher than an outer control system, then stable suitable control cannot be realized. Further, an outer control loop depends on an inner control loop, and has a response delayed with respect to the outer control loop.
Further, in a recent control theory, n control devices are designed at one time based on matrix calculation upon designing control devices for a multiplicity of state variables, but physical phenomenon relationships between the control devices and state quantities to be controlled become unclear, leading to the fact that the control system cannot be easily adjusted.